Jointed arm mechanisms for awnings are required to be of optimally flat construction, so that they are not esthetically disturbing in the retracted state. Such mechanisms may either be mounted totally unmasked, or may be inserted into a masking box in which the awning together with its mechanism disappears totally in the retracted position.
Awnings having a jointed arm mechanism are very rarely positioned to include in their extended position an angle of 0.degree. to a horizontal plane. They generally take an angle of around 10.degree.. The maximum downward inclination is generally about 45.degree.. It is difficult for a designer to produce mechanisms for awnings of flat construction and at the same time to make it possible for them to have a great inclination angle when they are extended. Frequently the terminal bar or sally tube provided at the free end of the joint arms closes, either itself or conjointly with a screen, the masking box which also may merely be in the form of a rain protection roof. If the inclination of the awning were selected somewhere between 45.degree. and 0.degree. according to clients' wishes, then obviously the screen and the terminal bar would also have this inclination, and consequently assume a different position to the rain protection roof or masking box.
Now, in order to permit a reasonably flat construction, but nevertheless always to have the same geometrical conditions in the region of the sally tube when the awning is fully retracted irrespective of the previous angle of inclination, the so-called tilting joint mechanisms have been developed. Irrespective of the desired angle of inclination, in this construction it is always guaranteed that the sally tube has the same position in the retracted state of the awning. Such mechanisms have an additional joint with the horizontal axis for each joint arm at its inner end region. When the awning shaft is rotated to extend the awning, the previously folded joint arms open in a substantially horizontal plane up to approximately 10.degree.. Only after this, the extensible part of the mechanism is overbalanced, mainly due to the weight of the terminal bar or sally tube, and the mechanism tilts downwards about the tilting joint by an angle corresponding to the adjusted value, for example somewhere between 10.degree. to 45.degree.. Devices of this type are disclosed in principle in U.S. Pat. Nos. 2,740,470 and 3,782,443.
Since such an awning can tilt downwards, it can also tilt upwards, particularly in the fully extended position. This may occur in the presence of gusts of wind. The forces which then act make the mechanism at least a case for repairs.
For this reason a device used in West Germany has become known, which prevents such cases by a tilt-up check device. In this case a short rod which extends in the bearing block body behind the inner joint of the inner joint arm, reciprocates in a brass slide which is guided in the body. The ratio of travel distances between the angular movement of the inner joint arm and the brass slide piece is such that immediately after the awning tilts, the inner edge of the slide piece slides over the external end face of a nut and then clamps this nut between itself and the rear wall of the body. The nut is screwed onto a screw bolt within the recess of the body. The farther the nut is unscrewed, the greater will be the inclination of the awning.
The screw bolt penetrates the rear wall of the recess in the body. It is a disadvantage of this known mechanism that it can be inclined only approximately up to 45.degree.. An inclination up to 90.degree., that is to say vertically downwards, would be desirable. This would be good for upper storey balconies in tall buildings. There are also commercial areas where it is a building regulation that awnings and blinds may only be released vertically downwards. With the known mechanism for the adjustment of merely 45.degree. a socket wrench is needed. Even with a socket wrench available, any adjustment can only be made in a quite specific intermediate position of the awning, which is difficult to do even for trained fitters.
A ladder is always necessary for such operation with a socket wrench. The screw bolt must be of steel. The body is always aluminum for considerations of weight and cost. The screw thread therefore acts as a saw on the aluminum casting. When the originally circular hole in the rear wall of the recess of the body has been sawn into a slot, the tilt-up check device will no longer operate. Although the purely external appearance of this tilt-up check device simulates a very robust construction, the slide piece bears upon the end face of the nut at only a few points. The slide piece has to be very robust because it has, in the projection of the screw bolt, an open-edged recess which is necessary, if it is desired to set inclinations of for example only 20.degree.. The slide piece is guided floatingly in translation in the body and consequently a strong robust brass block is necessary. The roll of the awning arranged in the rear of the box has to be carried past the body of relative cumbersome construction. This, and also the bulky construction of the tilt-up check device prohibit the design of a masking box lower than 19 cm.